I arrived in time to hear Michael Edwards of UCL make his usual point on these occasions which is, in effect, what about the greedy landlords, what about the evil property developers, what about the workers, and why can’t we all be more left wing? This was a challenge to a key theme of the report, which is that a degree of consensus has evolved across the disparate field that is the London housing sector – from commercial developers, to employers, to community groups, to boroughs and politicians of different shades – which, with the right kind of will and collaboration, could be translated into significant action.

There followed a discussion about how such an outcome might be arranged. One important point, made by the LSE’s Tony Travers from the chair, was that, in contrast to getting big transport schemes like Crossrail underway, big housing initiatives are less easy to give momentum to. That is largely because there are so many different, often very local, players involved. Such factors often include pressure on councillors from those they represent to obstruct housing developments in their back yards – Sir Mark, himself an elected politician, argued in a recent paper that planning decisions should be taken out of local representatives’ hands because their need for votes to often clashes with their duty to make decisions for the greater good. There was Age comes into this as well. Christine Whitehead, one of the LSE report’s co-authors, said: “We’ve got to get away from the situation where the only people who go to a planning inquiry are over 50.”

What else gets in the way? The LSE report floated the idea of a housing summit of all major interested parties, where differences could be thrashed out and a collective way forward agreed. Some of those present thought it not a bad idea, but not guaranteed to produce great results. Sorabji was among those to express gentle scepticism. “You won’t get the right people into the same a room unless they perceive a possible deal that might help them or that they can at least walk away from without it being too damaging,” he said. The problem, as he saw it, is that everything that might sustainably increase housebuilding tends to “push each of the individual players out of their comfort zones in terms of their political or managerial skill sets”. Soberingly, he added: “I don’t think the political push for more housing is actually very strong. There’s an awful lot more talk than there used to be, but there’s also a lot less commitment.”

The theme of politics constraining rather than enabling change was also pursued by Bowie. “Government is going to have to make some decisions which will not be popular,” he said. “Decisions at national level, decisions at local level.” It was time for the Green Belt taboo to make its customary appearance. “Every professional who’s been involved in these discussions says we need to ease up some of the restrictions,” Bowie said. “But politicians are making political decisions on this issue, because of public perceptions.” He’s right, of course. Why, only the other day housing minister Dominic Raab, MP for Esher and Walton, reaffirmed his belief that existing Green Belt safeguards should be maintained.

Then came Keith Exford, chief executive of the Clarion Housing Group, one of the G15 big housing associations. His take on the large gap between demand and supply was perhaps the most blunt, and had a particular resonance coming from someone whose job it is to actually put roofs over people’s heads. He agreed with previous speakers that inadequate public resources are a problem in London, but assured the assembled that there is “no absence of will” among the G15 members to build as many homes as possible. But, oh, the politics of it all. “Planning is now in purdah,” he said. “We won’t get any decisions until after May.” But the problem went wider. “Pretty much every ward is marginal in terms of what’s happening with development,” he said. And then there was a failure to deal with “the big things”, by which Exford meant “vested interests which hold back development”.

He had a list: “The Green Belt’s about dog-walkers, the suburbs are about preserving the idyll of low density.” Of Inner London, he said: “We have very low density estates which are reaching the end of their useful lives, but if you are seen to be doing something about re-providing those homes, it’s called ‘social cleansing’. And now we’re being told that we might have to start having ballots [before we can do it], which means private organisations surrendering control of their assets to the will of current occupiers rather than future occupiers”. He concluded: “There are real tensions in the system, some irreconcilable differences, which require political will to resolve. Are politicians brave enough to take decisions in the wider public interest, knowing that they are going to upset people? I’m sorry to say they are probably not.”

Exford wasn’t against the idea of a housing summit, but felt that if it didn’t deal with those controversies head on, little was likely to change as a result of it. Here was the glass half empty view of that nascent consensus the LSE report’s authors rightly identified. They are under no illusions about the difficulties. Exford simply pointed out some of the starker ones.

It all took me back to another piece of research, published in 2016 during the London Mayor election campaign that brought Sadiq Khan to power. A joint effort by Shelter and planning consultants Quod, it concluded that bringing overall housing supply in London up to 50,000 new homes a year would mean doing several things that would meet with resistance and – my word, not theirs – break taboos. Things like new garden cities outside London; more tall buildings; higher densities in the suburbs; more estate redevelopment; and, yes, re-designating some of the Green Belt. All these things present dilemmas. All are problematic. Yet if none of them are done, London’s housing shortage problem seems sure to keep on getting worse.

On London is run by Dave Hill, formerly the Guardian's award-winning London commentator, and written by him and an array of fellow Londoncentrics. It aims to improve the quality of coverage of London politics, development and culture.